<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>云层效果</title>

    <style>
    *{
        padding: 0;
        margin: 0;
    }

    li{
        list-style: none;
    }

    ul{
        margin-top: 100px;
        height: 400px;
        background-color: #f00;
        animation: name duration timing-function delay iteration-count direction fill-mode;
        animation: day-night 4s linear 0s infinite alternate;
        position: relative;
    }

    ul li{
        width: 400%;
        height: 100%;
        position: absolute;
        left: 0;
        top: 0;
    }
    @keyframes day-night{
        from{
            background-color: skyblue;
        }
        to{
            background-color: black;
        }
    }

    ul li:nth-child(1){
        background:url("Source/cloud_one.png");
        animation: one 2s linear 0s infinite alternate;
    }
    ul li:nth-child(2){
        background:url("Source/cloud_two.png");
        animation: one 20s linear 0s infinite alternate;
    }
    ul li:nth-child(3){
        background:url("Source/cloud_three.png");
        animation: one 10s linear 0s infinite alternate;
    }

    @keyframes one {
            from{
                margin-left: 0;
            }
            to{
                margin-left: -100%;
            }
     }

     @keyframes two {
            from{
                margin-left: 0;
            }
            to{
                margin-left: -200%;
            }
     }
        
     @keyframes three {
         from{
            margin-left: 0;
         }
         
         to{
            margin-left: -300%;
        }
     }

    </style>
</head>
<body>
    <ul>
        <li></li>
        <li></li>
        <li></li>
    </ul>
</body>
</html>